Fiber bodied composite cans have been adopted as a low cast container for numerous types of products. Such cans have found particular utility in packaging such food commodities as frozen juice concentrates, dry beverage products, soft drink mixes, coffee, tea and the like.
It has, however, been a constant problem to develop a fiber can which would permit easy opening with the various types of can openers presently in use. The paperboard material usually used in fiber bodied composite cans is softer, more compressible and thicker than the sheet metal material used in metal bodied cans. These different properties combine with the metal end conventionally used on a fiber bodied can to produce a crimp or seam which is somewhat wider and more compressible than the seam of a metal bodied can. Conventional can openers were originally designed for use with metal bodied cans which inherently have a narrower, stronger bead and also a hard metal wall to produce a positive supporting surface which prevents penetration into the body wall by the toothed driving wheel of the can opener. In addition, the hard metal wall maintains the driving wheel in properly oriented driving relationship with the underside of the can bead, thus preventing undercutting and slippage of the driving wheel with respect to said bead. With the softer fiber body of composite cans, the driving wheel engages both the head and adjacent outer body wall, and on certain can openers tends to penetrate into the body wall causing the driving wheel to undercut the bottom edge of the bead. This results in greater resistance to movement of the can opener around the periphery of the can, thereby making opening at best more difficult, and at worst impossible.
Early attempts to avoid this problem when utilizing containers having composite fiber bodies have involved the use of a metal collar embedded in the ends of the container so that the seaming and opening operation is substantially unchanged from that of a metal can. Typical of this approach is U.S. Pat. No. 2,367,419 issued to Morrell on Jan. 16, 1945. As can be seen from FIG. 8 of the Morrell patent, end closures are united to the metallic collars embedded in each end of the can wholly beyond the ends of the composite fiber body.
Another prior art approach to solving this problem has been to provide a circumferential score line in the metal end of the can either adjacent to or in the radius formed between the can end and the upstanding inner wall of the seam. Application of this technique to lightweight metal cans is disclosed in U.S. Pat. No. 3,073,480 issued to Henchert on Jan. 15, 1963. U.S. Pat. No. 3,397,809 issued to Ellerbrock on Aug. 20, 1968 discloses this same technique applied to composite fiber bodies cans. As is pointed out in the aforementioned references, the circumferential score line in the metal end reduces the cutting resistance encountered by the can opener blade. Accordingly, there is less tendency to slip as the can opener drive wheel travels about the periphery of the can.
While the foregoing prior art solution has afforded a degree of relief in the opening of composite fiber bodied containers having crimped metal ends secured thereto, they have by no means eliminated the difficulties posed by the wide variety of can openers presently in service.
Accordingly, it is an object of the present invention to further improve the reliability of opening of a composite container employing a crimped metal end with the various types of can openers presently in wide-spread use.
It is a further object of the present invention to provide such improved opening without materially increasing the cost of said composite containers or the metal ends secured thereto.
It is still another object of the present invention to provide a composite can having at least one crimped metal end secured thereto, which crimped metal end may be opened by means of a conventional can opener with a minimum of disfigurement to the exterior surface of the composite fiber body of the can.